Orbi RBR10 connection to samsung phone.

Thanks for the reply, much appreciated.
The Orbi router is in Router mode, as it always has been, and it shows the phone connected with 5G. I have cleared cache, reset all settings, and also done a factory reset, but with no improvement in performance. I suppose I could power down all satellites, then check the wifi speed from the Orbi router.
I don't remember which was the 1st symptom, whether speed or voice communication. I think possibly it was speed, because when trying to connect to a page, say FB, the screen would start blank, and the progress bar would freeze at the halfway point. Eventually, if I waited long enough, the page would finally load. Sometimes though (rarely), the phone works relatively normally, with clear voice and speed similar to my other Samsung phones.
My Orbi network is set up with fast roaming and daisy chain enabled. I have run tests with the phone in close proximity to several of the satellites, with the fastest connection being obtained when close to the satellite connected to the phone. Moving around the house, the phone does not switch to the closest satellite. Well, maybe it does if I would wait long enough.
I have run speed tests with the A54 located next to my old J727 and a Samsung A71. Sometimes, but very rarely the A54 will run slightly faster, but generally the A54 will show less than 5Mbps, while, at the same time, the other phones will be anywhere from 30 - 60Mbps.
Recently, I checked the starlink network speed close to the Starling router, it was 167Mbps. I immediately switch networks to the Orbi router, which showed the A54 as the connected device, and ran the test again, but got only 2Mbps.
In town, I ran the same test using the Puretalk (AT&T) cellular connection, and got 87Mbps.
I have no idea why the phone discriminates against the Orbi network, and it's difficult to argue with Samsung when they have tested the phone and found nothing wrong, instead claiming that the Mesh network is to blame, and asking me if I set up the network, as if to insinuate that I made a setup error. My answer to them is, as you wrote, that the phone connection was fine before the One UI update, but then, after updating, the problems started, so it has to be the update.
I've also told them that, to troubleshoot the problem, it would have to be done in my home where the problem exists. But, they will only do that if I pay for the home visit.